The percentage of leg injuries caused by head-on vehicle collisions is increasing and Underwriters Laboratories Inc. of the U.S. and Euro NCAP expect that a direct eccentric impact will increase the level of leg injuries. The impact-distributing structure of a vehicle floor is connected only in a fore-aft direction between a front side member and a center floor side member. This is because the conventional rear-wheel drive vehicle cannot have members at the lower part of the tunnel. Therefore, the connection of the impact-distributing structure with the side chamber box of the vehicle via a dash panel is compromised and, thus, experiences an enormous amount of change in vehicle body at the time of a head-on collision. As a result, the number and level of leg injuries to drivers is severe.